In some communications systems, e.g., cellular phone systems, frequency reuse is employed wherein cell cites will reuse a given frequency once they are deemed to be sufficiently geographically isolated from other cells using that frequency. For maximum capacity cell sites have been shrinking and cell sites that use the same frequency are getting closer to each other, thereby increasing co-channel interference. In other systems such as non-licensed ISM (Industrial, Scientific, Medical) bands where short range services such as Bluetooth and WiFi operate co-channel interference can be even more challenging.
One approach that is used to mitigate co-channel interference has been receiver antenna diversity. This will often enhance the desired signal and attenuate the co-channel interference. However, receiver antenna diversity may be costly and the extra antenna may be burdensome.